What do you do if you are fat and everyone hates you?

You need to accept yourself as you are and not let other people's opinions bother you. You may want to find out why people hate you and change what you can. It may be something other than your weight. What you can't change, is the other person's problem to deal with, not yours. You also need to realize that even though there may be people who do not like you, there are usually people that do like you, too, and you should develop friendships with those people.